@SoulofTwhitMulti Multiclass Eldritch Knight and Arcane Trickster: chapter 6 says slots as 1/3 lvl of chart, rounded down. Class lists use 1/3 rounded up, eg lv3 spell @ 13? Use chapter 6's calculation for your fighter/rogue's spell slots.

— Jeremy Crawford (@JeremyECrawford) January 21, 2015